The present invention relates to a vibration-canceling mechanism for an object subjected to a mechanical vibration, and to a head gimbal assembly (HGA) with the vibration-canceling mechanism.
In a magnetic disk drive apparatus, thin-film magnetic head elements for writing magnetic information into and/or reading magnetic information from magnetic disks are in general formed on magnetic head sliders flying in operation above the rotating magnetic disks. The sliders are supported at top end sections of suspensions of HGAs, respectively.
In operation, the HGA and therefore the magnetic head slider are driven or swung along a radial direction of the magnetic disk (track-width direction) by an actuator called as a voice coil motor (VCM), and thus a position of the magnetic head element with respect to a track in the magnetic disk is controlled.
The actuator, a drive arm coupled to the actuator and a suspension have inherent resonance characteristics with resonance frequencies different from each other, respectively. Thus, to the magnetic head slider attached at the top end section of the suspension, a mechanical vibration modified by a composite characteristic of these inherent resonance characteristics will be transferred.
In order to suppress such mechanical vibration modified by the composite resonance characteristic, conventionally, a resonance peak of an electrical drive signal was suppressed by at least one multi-stage filter mounted in a servo circuit of the actuator.
However, because such electrical vibration-suppressing method needed to provide the multi-stage filter, the servo circuit was complicated in configuration and thus the manufacturing cost increased. Also, since the mechanical vibration was suppressed by the electrical means not directly by a mechanical means, an efficiency for suppression was extremely low.
The suspension has in general a torsion mode resonance other than a lateral direction resonance in directions perpendicular to an axis in a plane of the suspension. A lateral component of the torsion mode resonance may often produce an off-track of the magnetic head element. Thus, the standard of the suspension severely limits an allowable amplitude of the lateral direction vibration. Due to this limitation of the lateral vibration amplitude, it is necessary to strictly manage the fabrication process for forming the shape of the suspension. In other words, it is very important to reduce a lateral component amplitude of a torsion mode resonance when designing a suspension.
It is therefore an aim of the present invention to provide a vibration-canceling mechanism and an HGA with the vibration canceling, whereby a mechanical vibration applied to an object can be suppressed with efficiency without greatly changing a conventional structure of the HGA.
Another aim of the present invention is to provide a vibration-canceling mechanism and an HGA with the vibration canceling, whereby a lateral component amplitude due to a torsion mode resonance can be effectively suppressed.
Further aim of the present invention is to provide a vibration-canceling mechanism and an HGA with the vibration canceling, whereby a configuration of a servo circuit of an actuator can be simplified.
According to the present invention, a vibration-canceling mechanism includes a vibration transfer member of a plane shape inserted between a vibration-origination system having at least one resonance frequency and an object to which a vibration is applied from the vibration-origination system. The vibration transfer member has a resonance frequency equal to or near the at least one resonance frequency of the vibration-origination system. A center of one end section of the vibration transfer member is coupled by a single arm section to a center of the other end section of the vibration transfer member. The one end section of the vibration transfer member is fixed to the vibration-origination system and the other end section of the vibration transfer member is fixed to the object so that an apparent vibration of the object is substantially canceled by a resonance of the vibration transfer member.
When the vibration-origination system resonates, the vibration transfer member also resonates. The one end section of the vibration transfer member vibrates in phase with the vibration-origination system but the other end section of the vibration transfer member vibrates in substantially inverted phase or deviated phase as the vibration-origination system. Therefore, the vibration transfer member operates so as to move a position of the object back to its original position that will be positioned when no resonance occurs, resulting the apparent vibration of the object to cancel.
As aforementioned, according to the present invention, only by additionally attaching the vibration transfer member with a simple structure, the mechanical vibration can be extremely effectively canceled without greatly changing a conventional structure of the HGA. Also, since a configuration of a servo circuit of the actuator can be simplified, a manufacturing cost of the magnetic disk drive apparatus can be reduced.
Also, since the vibration transfer member is configured in a plane shape, no bending process is needed and its characteristics can be adjusted only by executing a photo-etching process. Thus, a fabrication of the vibration transfer member can became very easy and also extremely high precision can be expected. The latter will present the minimum variation in the characteristics caused by a dimensional error.
Particularly, according to the present invention, because a center of one end section of the vibration transfer member is coupled by a single arm section to a center of the other end section of the vibration transfer member, not only an amplitude of a resonance mode for vibrating the object in lateral directions but also an amplitude of a lateral direction component of the torsion mode resonance can be effectively suppressed.
It is preferred that the vibration-canceling mechanism further includes a first damper layer provided between the other end section of the vibration transfer member and the vibration-origination system, for attenuating the vibration of the object. To the both surfaces of the first damper layer, vibrations of substantially inverted phase or deviated phase with each other are applied from the vibration-origination system and the vibration transfer member, respectively. Thus the first damper layer operates to restrict an excessive inverse-movement of the vibration transfer member so as to attenuate the amplitude of the vibration, and therefore the vibration of the object fixed to the other end section of the vibration transfer member is attenuated.
It is also preferred that the vibration-canceling mechanism further includes a second damper layer provided between the one end section of the vibration transfer member and the object, for attenuating the vibration of the object.
Preferably, the first and/or second damper layer is formed by a flexible resin adhesive adhered to the vibration transfer member and to the vibration-origination system.
Also it is preferred that the vibration-canceling mechanism is configured to apply a load in an up-and-down direction to the first and/or second damper layer. By applying the load, the damping effect of the damping layer will increase. The resonance frequency of a system consisting of the vibration transfer member and the damper layer varies depending upon a level of the applied load.
It is preferred that the vibration-origination system is a support member including a suspension, and that the object is a head slider with at least one head element attached to a top end section of the suspension.
It is further preferred that the head slider is fixed to one surface of the vibration transfer member and the suspension is fixed to the other surface of the vibration transfer member. Since the first damper layer is provided between the other end section of the vibration transfer member and the suspension, a gap space for inserting an adhesive can be automatically obtained between the vibration transfer member and the suspension. This results extremely easy assembling of the vibration transfer m with the suspension. Also, if the second damper layer is provided between the one end section of the vibration transfer member and the head slider, a gap space for inserting an adhesive can be automatically obtained between the vibration transfer member and the head slider. This results extremely easy assembling of the vibration transfer member with the head slider.
It is preferred that the head slider has a surface opposite to its air bearing surface (ABS), and that the vibration transfer member consists of a plane metal plate substantially in parallel with the surface opposite to the ABS.
It is also preferred that vibration transfer member includes the single arm section, the one end section a center of which is connected one end of the arm section and the other end section a center of which is connected the other end of the arm section.
It is further preferred that each of the one end section and the other end section has a plane rectangular shape.
It is further preferred that the at least one head element is at least one thin-film magnetic head element.
According to the present invention, furthermore, an HGA includes a head slider provided with at least one head element, a support member including a suspension and having at least one resonance frequency, and a vibration transfer member of a plane shape inserted between the suspension and the head slider to which a vibration is applied from the support member. The vibration transfer member has a resonance frequency equal to or near the at least one resonance frequency of the support member. A center of rear end section of the vibration transfer member is coupled by a single arm section to a center of a top end section of the vibration transfer member. The rear end section of the vibration transfer member is fixed to the suspension and the top end section of the vibration transfer member is fixed to the head slider so that an apparent vibration of the head slider is substantially canceled by a resonance of the vibration transfer member.
When the suspension (load beam) resonates to vibrate the flexure, the vibration transfer member also resonates. The rear end section of the vibration transfer member vibrates in phase with the flexure but the top end section of the vibration transfer member vibrates in substantially inverted phase or deviated phase as the flexure. Therefore, the vibration transfer member operates so as to move a position of the head slider back to its original position that will be positioned when no resonance occurs, resulting the apparent vibration of the head slider to cancel.
As aforementioned, according to the present invention, only by additionally attaching the vibration transfer member with a simple structure, the mechanical vibration can be extremely effectively canceled without greatly changing a conventional structure of the HGA. Also, since a configuration of a servo circuit of the actuator can be simplified, a manufacturing cost of the magnetic disk drive apparatus can be reduced.
Also, since the vibration transfer member is configured in a plane shape, no bending process is needed and its characteristics can be adjusted only by executing a photo-etching process. Thus, a fabrication of the vibration transfer member can become very easy and also extremely high precision can be expected. The latter will present the minimum variation in the characteristics caused by a dimensional error.
Particularly, according to the present invention, because a center of one end section of the vibration transfer member is coupled by a single arm section to a center of the other end section of the vibration transfer member, not only an amplitude of a resonance mode for vibrating the object in lateral directions but also an amplitude of a lateral direction component of the torsion mode resonance can be effectively suppressed.
It is preferred that the HGA further includes a first damper layer provided between the top end section of the vibration transfer member and the suspension, for attenuating the vibration of the head slider. To the both surfaces of the first damper layer, vibrations of substantially inverted phase or deviated phase with each other are applied from the flexure and the vibration transfer member, respectively. Thus the first damper layer operates to restrict an excessive inverse-movement of the vibration transfer member so as to attenuate the amplitude of the vibration, and therefore the vibration of the head slider fixed to the top end section of the vibration transfer member is attenuated.
It is preferred that the HGA further includes a second damper layer provided between the rear end section of the vibration transfer member and the head slider, for attenuating the vibration of the head slider.
It is also preferred that the first and/or second damper layer is formed by a flexible resin adhesive adhered to the vibration transfer member and to the suspension.
It is further preferred that the HGA is configured to apply a load in an up-and-down direction to the first and/or second damper layer. In the actual HGA, a load from the suspension is applied to the vibration transfer member and a resistance force from the recoding disk is applied to the head slider. Thus, forces in up-and-down directions are applied to the damper layer, and therefore the damping effect of the damping layer increases. The resonance frequency of a system consisting of the vibration transfer member and the damper layer varies depending upon a level of the applied load.
It is preferred that the head slider is fixed to one surface of the vibration transfer member and the suspension is fixed to the other surface of the vibration transfer member. Since the first damper layer is provided between the top end section of the vibration transfer member and the suspension, a gap space for inserting an adhesive can be automatically obtained between the vibration transfer member and the suspension. This results extremely easy assembling of the vibration transfer member with the suspension. Also, if the second damper layer is provided between the rear end section of the vibration transfer member and the head slider, a gap space for inserting an adhesive can be automatically obtained between the vibration transfer member and the head slider. This results extremely easy assembling of the vibration transfer member with the head slider.
It is preferred that the head slider has a surface opposite to its ABS, and that the vibration transfer member consists of a plane metal plate substantially in parallel with the surface opposite to the ABS.
It is also preferred that vibration transfer member includes the single arm section, the one end section a center of which is connected one end of the arm section and the other end section a center of which is connected the other end of the arm section.
It is further preferred that each of the one end section and the other end section has a plane rectangular shape.
It is still further preferred that the at least one head element is at least one thin-film magnetic head element.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.